Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 61: Liquid and Amorphous Metals V - Structure and structure formation
MM 61.2: Vortrag
Donnerstag, 3. April 2014, 16:00–16:15, IFW A
Dynamics of wetting and solidification for silicon droplet impacting a cold substrate — •Pierre-Yves Pichon1,2, Daniel Simons1, Dieter Herlach1, and Axel Schönecker2 — 1DLR, Institut für Materialphysik im Weltraum, Köln, Germany — 2RGS Development B.V., Bijlestaal 54 A 1721 PW, Broek op Langedijk, The Netherlands
The topic of this work is to examine the wetting dynamics of liquid silicon droplet during the impact on a cold substrate under well controlled conditions. This is motivated by the unusual behavior of the silicon-mold interaction during the crystallization of silicon wafers in the ribbon-growth-on-substrate (RGS) silicon casting process. Silicon droplets were melted in an electromagnetic levitation tool and released so as to impact a cold substrate with a defined amount of kinetic energy. The substrate temperature, wetting properties and roughness were controlled. During the spreading of the droplet on the substrate, the contact line velocity and the dynamic contact angle were recorded with a high speed camera. After the experiment, the interface between the solidified drop and the substrate was analyzed by microscopy. It was found that solidification and wetting strongly interact at the moving contact line. For example at lower substrate temperature, solidification prevents the system to reach the steady state wetting angle, because attachment kinetics of the atoms to the substrate is diffusion limited: solidification blocks the progression of the contact line. This can explain the behavior of the silicon in the RGS system and gives directions for further improvement of the process.